Mirror displays, which can serve as a mirror in a non-display state by using a half mirror plate with a half mirror layer provided on the viewing surface side of a display device, have been recently proposed for applications such as digital signage (e.g. Patent Literature 1). A mirror display is usable as a mirror in addition to as a display which is the original purpose. Specifically, when display light is emitted from the display device, the mirror display shows an image owing to the display light in a region where the display light is emitted from the display device. When no display light is emitted from the display device, on the other hand, the mirror display reflects the outside light and serves as a mirror in a region where the display light is not emitted from the display device.
Known examples of the half mirror layer include a reflective polarizer. A reflective polarizer reflects, among incident light components, a polarized light component parallel to the reflection axis of the polarizer and transmits a polarized light component perpendicular to the reflection axis thereof. The reflective polarizer accordingly can transmit a light component emitted from the display device to the viewing surface side as display light and can reflect an outside light component perpendicular to the polarization direction of the display light to the viewing surface side. A mirror display including a reflective polarizer as a half mirror layer switches the display mode and the mirror mode using such a principle.
In such a mirror display, when a reflective polarizer is bonded to a polarizer disposed on the viewing surface side of a liquid crystal display panel, for example, the flatness (irregularities) on the surface of the polarizer may cause distortion of a reflected image in a mirror mode. For solving this problem, a configuration has been proposed in which a reflective polarizer is bonded to a base material that is separately provided on the viewing surface side of a display device (e.g. Patent Literatures 1 and 2).